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be more suitable for image mapping at 1:150,000 rather than 1:50,000 
scale, and would not adequately record cultural detail. Mapsat is not 
a funded program and there is little likelihood that either NASA or the 
U. S. Geological Survey will build and operate it in the near future. 
The Survey hopes, however, that an eventual commercial operator will 
consider the parameters of the Mapsat system. 
The French SPOT system will also produce images with 10 m/pixel reso 
lution, and can produce stereo data with variable B/H ratio. It will 
therefore be able to produce topographic maps at about 1:150,000 scale 
in areas where ground control is available. The accuracy of spacecraft 
tracking and attitude are not known as a basis for predicting mapping 
capability without ground control. 
SPACELAB METRIC CAMERA EXPERIMENT 
One of the major advantages of the U. S. Space Shuttle is that the 
Orbiter vehicle returns to Earth after each mission. This makes it 
suitable for film camera systems where the requirement is to return the 
film to Earth for processing, rather than transmitting the information 
from the spacecraft to ground stations. 
Spacelab-1 is a joint venture between the European Space Agency (ESA) 
and NASA. It is presently scheduled for Shuttle Mission STS-9 in 
October 1983, at an altitude of 250 km. Among many experiments in 
Spacelab is the metric camera (MC) which is a modified Zeiss aerial 
camera having 30.5 focal length and 23 x 23 cm film format (Konecny, 
1979). The MC will be capable of producing ground resolution at approx 
imately 20 m/£p, suitable for reproduction as an image map at scale 
1:150,000, but not sufficient to show cultural detail with complete con 
sistency. Within the stereo model it will be possible to establish 
positions with about 10 m accuracy and contours at 40 to 80 m interval 
depending upon the B/H ratio employed. However Spacelab will be de 
pendent upon STDN for position and altitude and the IMU for attitude. 
In addition there is about 2° uncertainty in the alignment of the 
camera to the IMU because of spacecraft hot-dogging. Therefore abso 
lute position errors will approach 10 km and absolute elevation errors 
will be more than 100 m. Consequently it will still be necessary to 
employ ground control points to make maximum use of the Spacelab photo 
graphs. Nevertheless, the MC photographs will be a long step forward 
in topographic mapping from space. 
LARGE FORMAT CAMERA 
NASA has built a new mapping camera, referred to as the Large Format 
Camera (LFC), with focal length of 30.5 cm and film format of 
23 x 46 cm. (hence the designation Large Format) (Doyle, 1979). The 
camera will be installed with the long format dimension in the direc 
tion of flight. It can be operated with 10, 60, or 80 percent forward 
overlap which produces a B/H ratio of 0.6 at 60 percent overlap and 
1.2 at 80 percent overlap. It has automatic exposure control and for 
ward motion compensation which will permit high-resolution, slow-speed 
film to be used. The expected ground resolution with various film 
types is indicated in figure 1.